Laminated winding core for electromagnetic devices



June 26, 1962 w. J. BRADBURN, JR..Y ETAL 3,041,565

LAMINATED WINDING CORE FOR ELECTROMAGNETIC DEVICES Original Filed Feb. 25, 1954 M a w T M \\\\\m\&\ wwwmm mw\ H v \\E Pw L a mm; a 5 QU a i W P00 l.| w 1. 3 -m a w 6% 4& M AW H W ll m m United States Patent 2 Claims. (Cl. 336-217) This invention relates to laminated winding cores for electromagnetic devices such as magnetic amplifiers and more particularly to laminated cores of grain oriented metal. This application is a division of the applicants copending, but now abandoned, application, Serial No. 411,613, filed February 23, 1954 and titled Laminated Winding Core for Electromagnetic Devices.

As is well known, grain orientation in metal has a very substantial effect on the magnetic properties of that metal. Silicon steel sheets, for example, possess better magnetic characteristics when used with magnetic flux which is, nearly as possible, parallel to the rolling direction. In the past in forming laminated gapless cores from grain oriented material this difference has been partially overcome by making the bases of the cores relatively short and wide as distinguished from the relatively narrow and elongated legs of the cores, the orientation of the grain being substantially coincident with the longitudinal axes of the latter. This form of construction has required the use of a greater amount of metal and has also made it possible to provide only relatively long, narrow windows or openings in the center of the core. This in turn has seriously limited the size and number of windings which it is possible to place on such cores.

'It is therefore an object of this invention to provide laminated cores of a gapless construction utilizing grain oriented metal which require a smaller amount of metal to assemble and which still achieve electromagnetic characteristics which are the equivalent of the conventional forms of cores.

Another object is to provide a window of increased width in such cores, Without sacrificing desirable electrical characteristics.

Still another object is to provide cores of the character described which utilize laminations of relatively simple configuration which may be readily assembled.

Further objects and advantages of this invention will become evident as the description proceeds and from an examination of the accompanying drawings which illustrate several embodiments of the invention and in which similar numerals refer to similar parts throughout the several views.

In the drawings,

FIGURE 1 is a plan view of one form of core utilizing U-shaped laminations of grain oriented metal.

FIGURE 2 is a plan view of a strip of grain oriented material showing how substantially L-shaped laminations can be cut therefrom, together with suitable end pieces for use with such laminations.

FIGURE 3 is a plan view of a modified formv of core utilizing the L-shaped laminations shown in FIGURE 2, together with the end pieces disclosed therein.

FIGURE 4 is a plan view of still another form of core utilizing the L-shaped laminations disclosed in FIGURE 2, without the end pieces.

As mentioned above, it is customary when utilizing grain oriented material to give the core a configuration such that rather narrow, elongated legs are provided such as the legs and 12 shown in FIGURE 1. These legs, in turn, have the bases 14 and 16 extending therebetween which are relatively short and wide. This shape is desirable Patented June 26, 1962 when the orientation of the grain is in the direction of the arrows 18 since then the lines of flux within the core will normally be substantially parallel to the longitudinal. axes of the two legs 10 and 12 of the core, and therefore parallel to the direction of grain orientation, but will be substantially perpendicular to the direction of grain orientation in the bases 14 and 16. Thus although the permeability of the core would be considerably reduced in the bases thereof because of this grain orientation, this variation will be at least partially overcome by the greater width of the bases, and the rather close spacing of the two legs 10 and 12. This configuration of the laminations necessarily produces a window in the core which is relatively long and narrow, however.

The fact that there is a gap between the outer extremities of the arms of the U-shaped laminations in the form of core shown in FIGURE 1 of course has some effect on the permeability of the bases 14 and 16, and therefore also affects the dimensions which are required for these bases. As shown in FIGURE 1, utilizing a core having U-shaped laminations of a width substantially equal to 3a, with a being the width of an arm of the U-shaped laminations, the width b of each the bases 14 and 16, respectively, which has been found to be suitable if either greater than or equal to 2a. A core having these dimensional characteristics has been found to be satisfactory from an electromagnetic standpoint.

It has been found that an improved form of core can be formed which is similar to that shown in FIGURE 1, but in which the amount of lapping of adjacent laminations is considerably reduced. In order to avoid high flux concentration and saturation of the iron, it is necessary to have some surface overlap of the ends of the arms of one U- shaped piece with the base of the next adjacent piece, but it is not necessary to have a complete ,overlap as shown in FIGURE 1.

Referring specifically to FIGURES 2 and 3, substantially L-shaped laminations 50 and 52 may be utilized for purposes of improved core construction which laminates are cut preferably from a suitable strip 54 of grain oriented metal. Likewise, end pieces 56 may be also cut from the same strip 54 and these elements assembled as shown in FIGURE 3. The L-shaped laminations 50 and 52 may be disposed in two stacks with the bases 58 and 60 thereof at alternate ends and being partially overlapped by the outer extremities of the arms of the next adjacent L-shaped laminations. These two stacks, indicated generally by the numerals 62 and 64, may be joined by the end pieces 56 which may be disposed in association with the bases 58 and 60 between the arms of the corresponding laminations in each stack.

This construction, as shown in FIGURE 3, enables the window in the core to be widened. This is a distinct advantage since ordinarily a severe limitation exists in the size and number of windings or coils that can be placed on the legs of the core because of the narrowness of the window. At the same time the proper permeability is achieved in the bases of the core, indicated generally by the numerals 66 and 68, through the use of end pieces having a grain orientation as indicated by the arrow 70.

Still another form of core which can be fabricated from these L-shaped laminations is shown in FIGURE 4. This form differs fromthat shown in FIGURE 3 in that the end pieces 56 are eliminated and the corresponding laminations in each stack have their bases 58 and 60 disposed at opposite ends thereof. This enables the bases in one stack, at both ends thereof, to partially overlap the bases in the corresponding ends of the other stack.

In the form of core shown in FIGURE 3 the width of the end pieces 56 is preferably equal to b which is preferably equal to or greater than 2a. In the form of core shown in FIGURE 4, however, [2 is also preferably greater than or equal to 2a, whereas 0, the distance between each laterally adjacent base and arm extremity, is preferably between one-third and two-thirds a. The amount of overlap d, which is preferable for the extremities of the legs or arms of the L-shaped pieces over the bases of immediately adjacent laminations is greater than one-third a but less than or equal to b.

All of the cores described are believed to be improvements over the conventional forms of laminated cores. The benefits from the use of grain oriented material for the laminations have been attained, but at the same time some of the limitations previously inherent in the use of such materials have been overcome.

Iron-silicon alloys, nickel-iron-silicon alloys and silicon steel alloys have been found to be suitable as core materials in all of the various forms described.

In the drawing and specification, there have been set forth preferred embodiments of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. Changes in form and in the proportion of parts, as well as the substitution of equivalents are con templated, as circumstances may suggest or render expedient, without departing from the spirit or scope of this invention as further defined in the following claims.

We claim:

1. A laminated winding core for electromagnetic devices comprising a plurality of grain oriented metal laminations each said lamination having a base member and an elongated arm member of lesser width than said base member, said arm member partially overlapping the base of each vertically adjacent lamination by an amount substantially less than the height of said base member, with alternate laminations being disposed so that their bases are at opposite ends of said core, said laminations being so disposed in two vertical stacks with each set of laterally corresponding laminations of both stacks having their bases disposed opposite one another, and a plurality of end pieces disposed in two stacks, each end piece in each of said stacks being disposed in partially overlapping relation With the bases of one of said sets of laterally corresponding laminations and being disposed between the outer extremities of the arm members of another of said sets of laterally corresponding laminations.

2. A laminated winding core for electromagnetic devices comprising a plurality of substantially L-shaped laminations of grain oriented metal laminations each said lamination having a base member and an elongated arm member of lesser Width than said base member, said arm member only partially overlapping the base of each vertically adjacent lamination by an amount substantially less than the width of said base member in the direction of the width of the base member, with alternate laminations being disposed so that their bases are at opposite ends of said core, a plurality of end pieces, said laminations being so disposed in two vertical stacks with said end pieces in a magnetically coupled relation so as to form a closed flux path through said stacks.

References Cited in the file of this patent UNITED STATES PATENTS 2,316,928 Woodward Apr. 20, 1943 FOREIGN PATENTS 291,922 Switzerland Oct. 1, 1953 

